In sample preparation units, such as disclosed in pending application, Ser. No. 567,349 filed Apr. 11, 1975 now U.S. Pat. No. 4,000,976 it is desirable to utilize a pump which has the capabilities of simultaneously pumping numerous fluid samples into a plurality of individual receptacles disposed at predetermined stations. Because of rigid sanitary requirements to which such units are normally subjected, it is essential that the pump be readily disassembled for periodic cleaning. Furthermore, it is important that the seal means utilized in such a pump be easily replaced, when required, without necessitating substantial disassembly of the pump and/or resizing of the various components thereof. It is also desirable in a pump of this general type that the fluid flow within the pump interior produce a scrubbing effect on the surface defining the housing cavity and, thus, inhibit the formation of deposits or encrustations therein.